That rule means you can't have any other controls on screen, because it's not true for them and you can get into a semi-saved state. I believe it was just a nic

That rule means you can't have any other controls on screen, because it's not true for them and you can get into a semi-saved state. I believe it was just a niche designer factoid which sort of made it to reality by posts claiming that it's true. But it's way below the user uncertainty threshold to become a useful rule. I'm not against immediate effects on switches (or any other controls), but they must clearly signal the immediate action. E.g. I've seen some UIs presenting a short spinner on its button and delaying the colors and/or the shift.